Telephone system



(No Model.) E. BERLINER.

I TELEPHONE SYSTEM.

No. 255,239. PatentedMar. 21,1882:

mm iii T fnwentar.

N PETKRS. Pimlvulhugrnpher, Washington, D. G

UNITED STATES PATENT FIcE.

EMILE BER-LINER, OF BOSTON, MASSACHUSETTS.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 255,239, dated March 21, 1882.

' Application filed December 15, 1881. (No model.)

To all whom it may concern Be it known that I, EMILE BERLINER, of Boston, in the county of Suffolk and State of Massachusetts, have inven ted certain Improvements in Telephone Systems, of which the following is a specification.

Thisin vention relates to certain arrangements and switehingot' circuits for cases where a telephone-transmitter is used alternately with a local battery and induetioncoil, or with a linebattery and the coil excluded. Such acase may happen-for instance, when a subscriber to a telephone. system of one city intends to speak to a person in another city, using the same and no special transmitter. It is well known that the inducer-currents usually employed in telephone systems, though being cheap and very effective for ordinary intercommunication, are not efficient when theline whieh'they traverse offers extraordinary resistance, or if there is bad insulation, giving cause for leakage on the line. In this case induced currents are more apt to diffuse themselves through leakage to the ground than a battery-current of ordinary tension would under the same conditions, and hence it becomes desirable in telephonic intercommunication over long or badly-insulated lines to employ a large line-battery instead of a small local battery to be worked upon by the transmitter. In my system this line-battery is stationed at the central office. The arrangements, therefore, broadly comprise a system of telephonic intercornmunication in which the battery-tmnsmitter of a subscrib r to a system can readily be switched with the battery and induction-coil into a local primary circuit, and made to act upon a secondary circuit or into the line, to connect with a line-battery at the central office.

In the drawing, B isthe central office battery of one system, and N the central-office battery of another.

It and Q, are subscribers stations to the two respective systems.

A A are battery-transmitters; O O, batteries; T T, receiving-telephones.

p 1 I are induction-coils with two sets of con nectionsviz., P P primaries, S S secondaries. V

Y Y Z Z J J J J are switches, and E E are earth-plates.

In the ordinaryintercommunication between subscriber It, for instance, and another subscriber of the same system, his switches Y and Z are set upon buttons or positions 2 2. The transmitter will then be in local circuit with battery 0 and primary coil-connections P P, while the telephone T is thrown through the secondary connections S S to line and ground. If, now, however, this same subscriberR wishes to speak to subscriber Q of system N, it may be found that the resistance of the line L, connecting the systems B and N, may be too large or its leakage too great to allow the secondary impulses of the respective transmitters to effectively reach the other receiving-telephone. In this case it will be found necessary to bring the transmitter on the line in direct circuit with the telephones and a line-battery, and to accomplish this promptly my arrangements of circuits and switches will be found very practicable. In this instance all the switches are set upon the buttons or positions marked 1.

The central offices thereby switch a batteryin to the line, and the transmitters and receivingtelephones are now in one circuit passing through the central-office batteries.

What I claim is 1: A subscribers station of a telephone system consisting of the combination ot'a batterytransmitter, an induction-coil, a local battery, a reeeivirig-telephone, and switch Z, substantially as described, and so arranged that the line-circuit can by means of this switch be di-- 

